Spectrophotometric and spectrofluorimetric determination of etodolac and aceclofenac.

Two simple, sensitive and reproducible spectrophotometric and spectrofluorimetric methods were adopted for the analysis of the anti-inflammatory drugs, etodolac and aceclofenac. The first method is based on the formation of coloured complexes between the drugs and p-dimethylaminobenzaldehyde reagent (PDAB) in the presence of sulfuric acid and ferric chloride. Measurement of the absorbances was carried out at 591.5 and 545.5 nm for etodolac and aceclofenac, respectively. Regression analysis of Beer's plots showed good correlation in the concentration ranges 10-80 and 8-55 microg ml(-1), respectively. The second was the spectrofluorimetric method in which samples of etodolac in ethanol showed native fluorescence at a lambda = 345 nm when excitation was at 235 nm and samples of aceclofenac in the phosphate buffer pH 8 showed native fluorescence at lambda = 355 nm when excitation was at 250 nm. The calibration graph was rectilinear from 96 to 640 ng ml(-1) for etodolac and from 2 to 8 microg ml(-1) for aceclofenac. The proposed methods are applied successfully for the determination of the two drugs in bulk powder with a mean accuracy of 100.48+/-0.85 and 100.03+/-0.38 in the PDAB method and of 100.61+/-0.79 and 99.88+/-0.45 in the spectrofluorimetric method. Applicability of the proposed methods was examined by analysing dosage forms of the investigated drugs. Recoveries were 98.77-101.46 and 98.65-102.10% for the two methods, respectively and RSD values were 0.6-0.7 and 0.35-1.06% respectively.

Simultaneous determination of some multicomponent dosage forms by quantitative thin layer chromatography densitometric method.

In this study, simultaneous determination of naproxen with diflunisal (mixture I), paracetamol with chlorzoxazone (mixture II) and chlorphenoxamine hydrochloride with 8-chlorotheophylline and caffeine (mixture III) in multicomponent mixtures was conducted by a thin layer chromatography densitometric method. The mobile phase ethyl acetate: methanol: ammonia 25% (85:15:5 v/v) was used for the separation of the components of mixtures (I) and (II) with Rf values of 0.16 for naproxen, 0.4 for diflunisal, 0.77 for paracetamol and 0.32 for chlorzoxazone. Efficient separation of the components of mixture (III) was attained using ethyl acetate as mobile phase with Rf values of 0.12, 0.62 and 0.42 for chlorphenoxamine hydrochloride, 8-chlorotheophylline and caffeine, respectively. Linearity ranges, mean recoveries and relative standard deviations in calibration graphs of the proposed method were calculated. The method has been successfully applied to pharmaceutical formulations, sugar-coated tablets, capsules and suppositories. The results obtained were statistically compared with those obtained by applying the reported alternate methods.

Determination of meloxicam in bulk and pharmaceutical formulations.

Three sensitive and reproducible methods for quantitative determination of meloxicam (mel) in pure form and in pharmaceutical formulations are presented. The first method is high performance liquid chromatography by which the drug is determined in the presence of its degradation products over concentration range 100-500 microg x ml(-1) with mean percentage accuracy 100.13+/-0.53. The second method is based on measuring the absorbance of the formed neutral complex between basic methylene blue and mel in phosphate buffer (pH 8) at lambda=653.5 nm over concentration range 1-5 microg x ml(-1) with mean percentage accuracy 99.12+/-1.18. The third method is based on reaction between 2,3-dichloro-5,6-dicyano-p-benzoquinone resulting in the formation of an intense orange red coloured product after heating in a boiling water bath for 5 min. The coloured product exhibits an absorption maximum at 455 nm, over concentration range 40-160 microg x ml(-1) with mean percentage accuracy 100.53+/-1.04.

Determination of aceclofenac in bulk and pharmaceutical formulations.

Three sensitive and reproducible methods for quantitative determination of aceclofenac (AC) in pure form and in pharmaceutical formulation are presented. The first method is based on the reaction between the drug via its secondary aromatic amino group and p-dimethylaminocinnamaldehyde (PDAC) in acidified methanol to give a stable coloured complex after heating at 75 degrees C for 20 min. Absorption measurements were carried out at 665.5 nm. Beer's law is obeyed over concentration range 20-100 microg ml(-1) with mean recovery 100.33 +/- 0.84. The other two methods are high performance liquid chromatography (HPLC) and densitometric methods by which the drug was determined in the presence of its degradation products over concentration range of 20-70 microg ml(-1) and 1-10 microg per spot and mean recoveries are 99.59 +/- 0.90 and 99.45 +/- 1.09, respectively.

Stability-indicating methods for determining omeprazole and octylonium bromide in the presence of their degradation products.

Four stability-indicating assays were developed for determining omeprazole and octylonium bromide. Omeprazole is photodegraded and estimated in the presence of its degradation products sulphenamide (I) and benzimidazole sulphide (II) by 2 methods. The first method depends on use of first-, second-, and third-derivative spectrophotometry at 290.4, 320.6, and 311.6 nm, respectively. The second method is based on applying the charge-transfer technique with chloranil as pi acceptor to form a complex with omeprazole, the absorbance of which is measured at 377 nm. These methods determine omeprazole in concentration ranges of 5-20 micrograms/mL by first-, second-, and third-derivative spectrophotometry and 10-50 micrograms/mL by charge-transfer complexation with mean accuracies of 99.92 +/- 0.73, 99.71 +/- 1.02, 99.64 +/- 0.66, and 100.24 +/- 0.81%, respectively. Octylonium bromide is determined by a densitometric method using thin-layer chromatography in the presence of its degradation products p-[2-(n-octyoxy)benzoyl]-aminobenzoic acid (III) and diethyl-(2-hydroxyethyl)-methyl ammonium bromide (IV) without any interferences. Alternatively, octylonium bromide is evaluated by a colorimetric method using the acid dye rose bengal. The ion pair formed is extracted in chloroform at pH 4, and its absorbance is measured at 562 nm. These methods determine octylonium bromide in the presence of its degradation products in concentration ranges of 0.1-0.5 microgram/microL by densitometry and 4.5-22.5 micrograms/mL by colorimetry, with mean accuracies of 100.21 +/- 0.93 and 99.73 +/- 0.89%, respectively. The suggested methods were used to determine drugs in bulk powder, laboratory-prepared mixtures, and pharmaceutical dosage forms. Results were compared statistically with those obtained with reference methods.

Colorimetric analysis of some diuretic drugs: hydrochlorothiazide and spironolactone.

Two convenient spectrophotometric methods were developed for the determination of hydrochlorothiazide and spironolactone. A specific colour reaction for the determination of hydrochlorothiazide is reported. One method is based on the reaction of hydrochlorothiazide with n-butylamine and cobaltous chloride in anhydrous methanol. A blue-violet colour is produced and is measured at 570 nm. A highly selective colorimetric method was adopted for the analysis of spironolactone by reacting with isoniazid forming a coloured hydrazone derivative and subsequent measurement of the coloured product at 405 nm.